Fuse computer



EWWQEE June 14, 1955 L. A. NETTLETON ET AL FUSE COMPUTER Filed April 10, 1946 INVENTORS. LEROY A. NETTLETON CARLTON W. MILLER ATTORNEY United States Patent FUSE COMPUTER Leroy A. Nettleton, Ridgewood, N. J., and Carlton W. Miller, Boston, Mass., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application April 10, 1946, Serial No. 661,024

1 Claim. (Cl. 235-615) This invention relates to mechanical-electrical computing systems and more specifically to a computer determining the fuse setting for a projectile.

A gun director, in controlling the fire of a gun, must solve two problems. First, it must tell the gun how far ahead of the target it must aim in order to hit it at some future time. This solution involves factors such as; target range, range rate, vertical angular rate, horizontal angular rate, and ballistics of the gun. The solution is dependent upon some time interval between the observation of the target position and arrival of the projectile in the vicinity of the target. The second problem of the gun director is to provide a fuse setting for the projectile so that it will burst in the vicinity of the target.

The solution of the fuse setting problem involves solving the following equation:

in which:

Tg is the dead time in seconds between setting the fuse and firing the projectile.

This equation corrects the fuse setting for the motion of the target during the dead time Tg. The desired quan tity is the fuse setting time F. The other terms may be obtained from the other components of the gun director or manually inserted as mechanical motions or positions.

The object of this invention is to provide a mechanicalelectrical computer capable of rapidly solving the above equation.

Another object is to provide a device capable of combining mechanical motions and electrical values to produce an output which is the solution of a mathematical equation involving the original values.

Other objects and applications will be apparent from the following specification when considered with the accompanying drawing the single figure of which shows a schematic diagram of a particular embodiment of this invention.

The function of the circuit shown in the accompanying diagram is, as described before, to solve the fuse setting equation for the value of F. The terms G, f(G), U, tan D, tan V, and dR are supplied from other com- Patented June 14, 1955 ponents of the gun director as mechanical motions. The terms Tg and Pi are supplied as mechanical motions from manual adjustments.

Referring now to the accompanying diagram a source of alternating current energy is connected to the primary of transformer 10 at terminals 11. Transformer 10 has a single secondary winding with a center tap 14 which is grounded. Thus equal voltages of opposite phase are obtained between terminals 12 and 13 and the grounded center tap 14. A linear potentiometer 15 has its movable contact driven by the mechanical motion f(G). Potentiometer 15 is connected through appropriate fixed value end resistors 16 and 17 across terminals 13 and 14. A second linear potentiometer 19 has its movable contact driven by the mechanical motion U. Potentiometer 19 is connected with appropriate fixed value end resistors 18 and 20 from the movable contact of potentiometer 15 to terminal 14. The mechanical motion tan D is connected to the movable contact of potentiometer 22. Potentiometer 22 has a grounded center tap and the resistance element is non-linear, tapering as the square of the displacement from center. The ends of potentiometer 22 connect to terminal 12 through fixed value resistors 23 and 24. The mechanical motion tan V is connected to the movable contact of potentiometer 25 which has a grounded tap. The resistance element of potentiometer 25 is also tapered as the square of the displacement from center. The ends of potentiometer 25 are connected through fixed value resistors 26 and 27 to terminal 12. Potentiometer 28 has a linear resistance element and the movable contact is connected to the motion dR. Potentiometer 28 is connected through fixed value resistors 29 and 30 to terminals 12 and 13 respectively.

The movable contacts of potentiometers 19, 22, 25 and 28 connect through fixed resistors 32, 33, 34, and respectively to the primary winding of transformer 40. The other end of the primary winding of transformer is grounded. A potentiometer 42 having a linear resistance is connected across the secondary winding of transformer 40. A potentiometer 43 is connected through fixed value end resistors 44 and 45 across the secondary of transformer 40. The movable contact of potentiometer 43 is grounded and is driven by motion F j which is a manual adjustment. A center tap on potentiometer 43 is connected to an off center tap on potentiometer 42 and also through capacitor 52 to one side of the secondary of transformer 40.

The movable contacts of potentiometer 22, 25, and 28 are connected through fixed resistors 36, 37 and 38 respectively to one end terminal of a potentiometer 46. The other end of potentiometer 46 connects through fixed value resistor 47 to ground. Also connecting from the junction of resistors 36, 37 and 38 to ground is a capacitor 53, in parallel with resistor 41. A transformer 48 has its primary winding connected between the movable contacts of potentiometers 46 and 42. The secondary of transformer 48, one side of which is grounded, connects to a servo amplifier 49, which supplies power to a motor 50. The shaft of motor 50 connects to a mechanical differential 51. The mechanical differential 51 is also supplied with mechanical motion G. The output shaft of differential 51 drives the movable contact of potentiometer 42. The shaft rotation of motor 50 represents the solution F of the equation.

In the operation of this circuit to solve the equation of fuse setting, the values of the mechanical motions are converted to values of electrical potential by the potentiometers. As certain of the values, as used in the equation, are negative, both positive and negative potentials must be present in the circuit. This is accomplished in the alternating current circuit by providing alternating potentials of opposite phase from the secondary of transformer 10. Thus the potential between terminal 12 and ground may be termed E+ and between terminal 13 and ground as E.

The product f(G)U in the equation is obtained by potentiometers 15 and 19. As this product has a negative sign in the equation, the potentiometers 15 and 19 are energized by the E potential between terminal 13 and ground. The potential at the movable contact of potentiometer 15 represents the term f(G). This potential is applied across potentiometer 19 so the potential at the movable contact of potentiometer 19 will represent the product f(G)U. This potential is applied through resistor 32 to the primary of transformer 40. The resistors 32, 16, 17, 18 and 20 are included to limit the range of the potentiometer, prevent interaction between potentiometers, and provide the algebraic constant. Thus the current through the primary of transformer 40 due to this network represents the total term The function (tan D) is provided by potentiometer 22 and associated fixed resistors 23 and 24. As the function (tan D) may be zero but never negative the center tap of potentiometer 22 is grounded and the ends are both returned to the E+ terminal 12. The function is squared by the square function taper of the potentiometer resistance. Resistors 23 and 24 limit the range of potentiometer 22. The potential at the movable contact of potentiometer 22 is therefore proportional to (tan D) This potential is applied through resistor 33 to the primary transformer 40 and supplies a current proportional to .l6(tan D) This potential from potentiometer 22 is also supplied through resistor 36 to potenti- I ometer 46 providing a current proportional to (tan D) The function (tan VK) is provided by potenti ometer 25, with a tapered resistance identical to potentiometer 22. However, the constant K is provided by grounding a point off center of the potentiometer 25. The voltage at the movable contact is proportional to (tan V-K) and is applied through resistor 34 to transformer 40. This provides a current in the primary of transformer 40 potential to .l6(tan VK) A potential is also supplied from potentiometer 25 through resistor 37 to potentiometer 46 providing a current proportional to (tan VK) The mechanical motion dR is applied to the movable contact of potentiometer 28 giving a potential proportional to dR. Resistors 29 and 30 limit the range of po The voltage across the secondary of transformer may also be represented by this expression. This voltage is applied across potentiometer 42, so the potential at the movable contact Will be the above expression multiplied by the mechanical position of the movable contact. To provide a reference for this potential the movable contact of potentiometer 43 is grounded. By adjusting potentiometer 43 the reference point may be moved. Thus the potential at the movable contact of potentiometer 42 becomes the above expression muliplied by the sum of the mechanical motions of the contacts of potentiometers 42 and 43. If potentiometer 42 is driven by a motion (GF) and potentiometer 43 by a motion Fj, the output potential at the contact of potentiometer 42 in respect to ground will be:

213922 .l6(tan V K) 825 which is the expression for one side of the fuse setting equation.

The current applied to potentiometer 46 is the sum of the currents supplied through resistors 36, 37 and 38. Thus the voltage across potentiometer 46 and resistor 47 will be proportional to the sum of the currents. The mechanical motion applied to the movable contact of po tentiometer 46 is the manual adjustment for dead time Tg, so the voltage at the contact will be the product of Tg and the potential across the potentiometer 46. This product will be the expression for the right side of the fuse setting equation or:

The expressions for the two sides of the fuse setting equation now exist as voltages at the movable contacts of potentiometers 42 and 46. To satisfy the equation these potentials must be equal. If the equation is not balanced a voltage will appear across the primary of transformer 43. The magnitude and phase of this voltage will be dependent upon the degree and sign of the equation unbalance. Thus this voltage becomes an error signal and is coupled by transformer 48 to the servo amplifier 49. Amplifier 49 supplies power to motor 50 causing it to rotate. This motor rotation is coupled to mechanical differential 51 where it is mechanically subtracted from the mechanical motion G to give the expression (GF). (G-F) appears as a mechanical motion at the output shaft of mechanical differential 51 and is coupled to the movable contact of potentiometer 42. An error signal will exist across the primary of transformer 48 until motor 50 has rotated far enough to cause the potential at the movable contact of potentiometer 42 to equal the potential at the contact of potentiometer 46. The rotation of motor 54 thus balances the fuse setting equation and becomes a mechanical motion proportional to the term F, the desired solution.

Resistor 41 in parallel with potentiometer 46 and resistor 47 acts only to provide proper constants in the resistance network. Capacitors 52 and 53 serve to equalize the phase shift in the resistance networks caused by the transformer 40. The value of capacitors 52 and 53 will vary with change in type of transformer used. Typical values of circuit components used in this circuit for solution of the fuse setting equation are listed below.

Circuit component values:

10 transformer primary v. 60 cycles sec.

til-transformer 1:1 ratio.

15 "ohms" 2,000 32 ..0hms- 38,250 16 v d0 450 33 d0 482,600 17 do 950 34 do 482,600 18 do 17,100 35 do 78,590 19 do 5,000 36 do 129,850 20 d0 17,100 37 do 129,850 22 dO 12,090 38 d0 143,350 23 do 6,799 ,41 1..do 38,000 24 do. 6,799 42 do 60,000 25 do 11,432 43 do. 50,000 26 d0 8,591 44 do 75,000 27 dO 9,933 45 do 188,750 28 dO 5,000 46 do 20,000 29 do 7,500 47 do 15,000 30 do 6,667

The voltage per degree appearing on potentiometer 42 tends to vary over a wide range effecting the sensitivity of the servo amplifier 49 and thus the accuracy of the final balance. To maintain constant sensitivity the gain of the servo amplifier 49 is controlled by the voltage across the primary of transformer 40.

The invention is not limited to the solution of the particular equation described and shown but many other applications of the principles involved may easily be devised. The novel features include, the use of potentiometers having tapered resistance elements to convert mechanical information into electrical information and perform mathematical operations thereon, the use of resistance networks to combine electrical information according to an algebraic equation, and the use of a servo system and potentiometer to balance a mathematical equation existing as electrical information.

This invention is not to be limited to the details of operation and design disclosed and illustrated in the accompanying drawing except as appears hereafter in the claim.

What is claimed is:

A mechanical electrical computing circuit for solving a fuse setting equation comprising, first, second, third, fourth, fifth, sixth, and seventh potentiometers, a mechanical differential, said potentiometers and differential having each a mechanical input proportional to a known term of said equation; a source of alternating current, a first transformer having a primary winding connecting to said current source, the secondary of said first transformer having a grounded center tap and supplying equal voltages to a first and second terminal, said first potentiometer being connected from said second terminal to ground, said second potentiometer being connected from the movable contact of said first potentiometer to ground, said third and fourth potentiometers being connected at their ends to said first terminal, the resistance element of said third and fourth potentiometers having a grounded center tap and being tapered as the square of the displacement from center, said fifth potentiometer being connected between said first and second terminals, a second transformer having a primary and secondary winding, a first, second, third, and fourth fixed resistor, said resistors being connected from said second transformer primary to the movable contacts of said second, third, fourth, and fifth potentiometers respectively, said second transformer primary winding being connected to ground, an eighth potentiometer, said sixth and eighth potentiometers being connected in parallel across said second transformer secondary winding, said sixth potentiometer having a tap connected to a tap on said eighth potentiometer, the movable contact of said sixth potentiometer being connected to ground, the movable contact of said eighth potentiometer being mechanically actuated by the output of said mechanical differential, a fifth, sixth, and seventh fixed resistor, said resistors being connected from said movable contacts of said third, fourth, and fifth potentiometers respectively to one end terminal of said seventh potentiometer, said seventh potentiometer being connected at its other end terminal to ground, a third transformer, the primary of said third transformer being connected between the movable contacts of said seventh and eighth potentiometers, a servo amplifier being connected to the secondary of said third transformer, and a motor, said motor being connected to the output of said servo amplifier, the mechanical output of said motor being connected to supply one input to said mechanical differential, said motor mechanical output being proportional to the solution of said fuse setting equation.

References Cited in the file of this patent UNITED STATES PATENTS 2,385,334 Davey Sept. 25, 1945 2,404,387 Lovell et al Sept. 24, 1946 2,414,819 Lakatos Jan. 28, 1947 2,426,658 Wooldridge Sept. 2, 1947 2,432,504 Boghosian et al Dec. 16, 1947 2,479,909 Darlington Aug. 23, 1949 FOREIGN PATENTS 164,765 Great Britain June 23, 1921 

